1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a micro electromechanical system (MEMS) device package and a method for manufacturing the same.
2. Description of the Related Art
MEMS is the integration of sensors, micro actuators, gyroscopes, precise machine parts, etc. using semiconductor processing technology. As a high level of precision, product uniformity, and superior productivity required for semiconductor processing are applied to MEMS, MEMS is recognized as a technology capable of improving performances of products while reducing costs.
MEMS devices such as acceleration sensors, angular velocity sensors, resonant gyroscopes, or the like are packaged for the purpose of enhancing protectability and/or sensitivity thereof. As high density and miniaturization of MEMS devices have been realized due to the rapid development of technologies for manufacturing MEMS devices, it is also required for packages to be correspondingly miniaturized. For this purpose, Wafer Scale Package (WSP) application for packaging devices in a wafer state is frequently attempted.
FIG. 1 is a cross-sectional view schematically showing an example of a conventional MEMS device package. As shown in the drawing, a device substrate 1 is provided with a MEMS active device 2, and a glass closure substrate 3 is joined to the device substrate 1 for protecting the MEMS active device 2. The MEMS active device 2 typically has a spring structure and a stage supported by the spring structure.
In addition, internal electrode pads 5 are formed on the device substrate 1, wherein each of the internal electrode pads is positioned on the opposite side of the MEMS active device 2 and electrically connected to the MEMS active device 2. A cavity 4 is formed under the glass closure substrate 3 for providing a space for receiving the MEMS active device 2, wherein the glass closure substrate 3 and the device substrate 1 are anodic-bonded to each other.
In addition, via holes 6 are formed on the opposite sides of the glass closure substrate 3, and external electrode pads 7, which are connected to the internal electrode pads 5, are formed through the via holes 6. Here, the via holes 6 are formed through a sandblasting process, and the external electrodes 7 are formed by filling a metallic material (typically Al) in the via holes 6 through a sputtering process. The external electrode pads 7 are connected to a signal line on a circuit board not shown in the figure through a wire, a bump or the like.
However, a conventional MEMS device package as described above inevitably has a thick glass closure substrate 3 due to the bonding structure between the glass closure substrate 3 and a silicon-based device substrate 1 and the manufacturing process of the MEMS device package, whereby there is a limit in reducing the size of the package due to the via holes 6 in the glass substrate 3. In other words, due to a large size and a high height, such a conventional MEMS package occupies a large volume in an apparatus incorporating it, thereby causing the miniaturization of the apparatus to be hindered.
Furthermore, because such a conventional MEMS package employs a closure substrate 3 formed from glass, the processes for forming the via holes 6 and the external electrode pads 7 are difficult to perform and require much time, thereby causing a decrease in yield and productivity.
Such a conventional MEMS package also has a problem in that the MEMS active device 2 may be deformed or damaged due to high temperature (typically about 460° C.) at the time of anodic-bonding and has basic stress due to the difference in thermal expansion coefficient between the glass closure substrate 3 and the silicon-based device substrate 1.
Moreover, a problem of reliability may be presented because the connection of a circuit by means of the internal electrode pads 5 formed from a silicon material and the external electrode pads 7 formed from a metallic material produces a very high inductance in relation to RF signals of high frequency and electrical contact resistance at the contact parts, thereby causing a high loss in signal.